International relations are not a black and white thing. Some of our "allies" do unspeakable things, including genocide. Obama made a deal with some bad people, and Trump tore it up. It's possible to strike a good deal with bad people, and Trump was on the verge of doing that so that we could get closer to stability in the region.
If we learned anything from Iraq, it's that there are high costs and long lasting consequences for trying to be the hero on every corner of the globe. Yes the world is better off without Saddam, but was the invasion truly necessary to get rid of him? Could that not have been achieved with soft power? With diplomacy? By propping up his internal adversaries?
The goal was to prevent Iran from having nukes, and I fail to see how or why American intervention is the only way to achieve that. If you believe that's the same thing as "cheering for the bad man to stay in power forever," then that says more about you than it does about me.